bug#39815: Sharing the store between a host and a guest

[Leo Famulari <leo@famulari.name>]

Hi Damien,

Currently Guix does not include tools to support your use case of
"writable and shared /gnu/store in the VM".

`guix system container` might be useful but the isolation guarantees are
weaker than with QEMU. However, QEMU is not bulletproof either.

The recommended way to get a writeable store in a VM is to use `guix
system vm-image`, copy the image out of /gnu/store, make it writeable
with `chmod`, and then run it in QEMU. This will not share the store
with the host.

As you found, what you get with `guix system vm` is read-only. Even
though you copied build-vm.sh out of /gnu/store, it is just a shell
script that refers to immutable data in the host /gnu/store.

In order to share the store with a VM, you would need to also share the
store database — at least /var/guix/db if not all of /var/guix — and
also use the host's guix-daemon.

It would be great to support your use case but I don't think anyone has
worked on it yet.

Leo